1. Field of the Invention
The present invention relates to a liquid crystal display device. The invention relates, in particular to a liquid crystal display device having an auxiliary wiring pattern that can make electric characteristics to be observed. The invention also relates to a method of monitoring electric characteristics of bus-lines of a liquid crystal display device by using s.
2. Description of Related Art
Such a type of liquid crystal display device is disclosed in, e.g. a reference of Japanese Patent Application Laid-Open No. 233,514/92 (or the corresponding application, U.S. Pat. No. 5,349,226).
In this reference, there is described a liquid crystal display device having an active matrix board provided with an array of thin film transistors formed in matrix on an insulative substrate, wherein portions of gate bus-line and source bus-line of the thin film transistor array form contact pads for probing of which metallic parts are exposed to the exterior. According to this configuration, under actual operating conditions of the liquid crystal display device, it is possible to easily make a contact of a probe for monitoring a signal waveform of the bus-line with the metallic part, visually, whereby the operation can be checked with no disadvantages including destruction and cut-off of the bus-line.
However, in the prior art, the metallic part as the contact pad, which has been formed in the vicinity of the bus-line on the substrate, is forced to be exposed to the exterior at least when monitoring the waveform. Therefore, the metallic part can suffer some damage due to its contact with the probe, so that the damage may promote metallic corrosion to lead influence such as deterioration of electrical conductivity of the bus-line.
The prior art is a technique that allows only a specific bus-line having been provided with a contact pad to be monitored. Accordingly, it has to always provide a bus-line to be monitored in waveform with a contact pad, and even when all the bus-lines are provided with contact pads beforehand, it may lead a disadvantageous condition that possibly unnecessary bus-lines to be waveform-monitored may be wasted, may cause the above-mentioned corrosion problem and may be inflexible.